Inside the Machine

The brain of the computer

At the heart of every computer is the CPU, the central processing unit, which runs programs by carrying out instructions. Inside it are parts that each do a job: one does the calculations and logic, one directs the flow of work, tiny fast stores hold values in use, and a clock keeps everything in time. The CPU works with memory: RAM holds what is in use right now, while ROM holds the instructions to start the computer. This module covers the CPU parts, the cycle it repeats, what makes it fast, and how memory and storage differ.

Architecture words

Learn these four parts before you sort any job, because the exam expects the exact names of the components inside the processor.

RAM against ROM

The two kinds of main memory are easy to confuse. The key differences are whether they keep data when the power is off and what they are used for.

How to reason about the parts

For the components, ask what each one is FOR: which part does the sums, which directs the work, which stores a value for an instant, and which sets the pace. For the cycle a processor repeats, name the parts it uses as it goes. To judge memory, ask whether it must survive the power being switched off. To choose storage, do not list features in the air: match the type to what the user actually needs, such as speed, size or being easy to carry.

Match the CPU part to its job

What does RAM do?

Which statement best describes RAM?

• It holds programs and data in use now and loses them when the power is off.
• It permanently holds the instructions that start the computer.
• It stores files permanently like a hard drive.
• It does the calculations for the processor.

What makes a CPU faster?

Select the TWO factors that can make a CPU perform faster.

• A higher clock speed
• More cores
• A brighter case colour
• A heavier computer

Count the extra cores

A quad-core processor has 4 cores. A dual-core processor has 2 cores. Subtract to find how many more cores the quad-core processor has than the dual-core. What is the answer?

Order the cycle

Put the stages of the fetch-decode-execute cycle in order, earliest first.

• Fetch the next instruction from memory
• Decode the instruction to see what it means
• Execute the instruction, using the ALU if needed
• Repeat the cycle for the next instruction

Complete the facts

The part of the CPU that does calculations and logic is the _____. The part that directs operations is the _____. Memory that loses its contents when the power is off and holds what is in use now is _____. Memory that keeps its contents and holds the start-up instructions is _____.

Match the storage to the need

Spot the true architecture facts

Tap the TWO statements that are true about how a computer works.

• The ALU carries out calculations and logic
• RAM loses its contents when the power is switched off
• ROM loses its contents when the power is off
• The control unit does all the calculations

Choose the part or storage

Read each case and choose the best answer.

• A program needs a sum worked out and a logical comparison made. Which part of the CPU does this?
• A video editor needs a drive that is very fast and tough enough to carry around in a laptop. Which storage suits best?
• A user wants to reach the same files from a phone, a tablet and a laptop wherever they are. Which storage suits best?

Explain how the computer works

Explain the main parts of the CPU, the cycle it repeats to run a program, and the difference between RAM and ROM.

• Name two parts of the CPU and what each does
• Explain the fetch-decode-execute cycle in order
• Explain the difference between RAM and ROM
• Give one factor that makes a CPU perform faster